(I don't know about Dreamwidth development, but I work as a Perl consultant, I give courses in it and I follow the Perl development).
Backwards compatibility is taken very seriously by the Perl developers. There are new features in 5.10, 5.12 and 5.14, but you have to specifically ask to have them activated before you can use them. In general, the most likely reason to get problems when going up to a newer Perl version is that you've accidentally relied on buggy behavior that got fixed, or that you're using a feature that got deprecated (one major version will warn before anything is removed, so only really a surprise if you jump several major versions in one go).
It is much more likely that you'll have problems when upgrading any external modules you rely on, but you'll probably run into that one even if you stay at an old Perl version.
My recommendation: If you just want a newer more-supported Perl version, aim for 5.12.3. I've moved two projects from 5.8.9 to 5.12.3, and it was very smooth both times. If significant work with non-latin alphabets and/or IPv6 is in your future plans, wait a couple of months and try 5.14.1 instead.
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Backwards compatibility is taken very seriously by the Perl developers. There are new features in 5.10, 5.12 and 5.14, but you have to specifically ask to have them activated before you can use them. In general, the most likely reason to get problems when going up to a newer Perl version is that you've accidentally relied on buggy behavior that got fixed, or that you're using a feature that got deprecated (one major version will warn before anything is removed, so only really a surprise if you jump several major versions in one go).
It is much more likely that you'll have problems when upgrading any external modules you rely on, but you'll probably run into that one even if you stay at an old Perl version.
My recommendation: If you just want a newer more-supported Perl version, aim for 5.12.3. I've moved two projects from 5.8.9 to 5.12.3, and it was very smooth both times. If significant work with non-latin alphabets and/or IPv6 is in your future plans, wait a couple of months and try 5.14.1 instead.